Anesthesia for fetoscopic intervention.

This is the first case report on anesthesia for fetoscopy performed in Saudi Arabia. Epidural anesthesia was given to the mother in her late second trimester for the fetoscopic intervention. The anesthesia related issues such as physiological and anatomical changes in pregnancy, tocolytic medications and their interactions with anesthesia, anesthetizing/sedating the primary patient are discussed.

INTRODUCTION

Having been performed in only a few centers world-wide fetal surgery is a relatively new innovation that encompasses prenatal interventional procedures on the fetus with the aim of rectifying birth defects. The sub-discipline of fetoscopic intervention refers to procedures that are minimally invasive for both mother and fetus and that are performed with the aid of real-time video to view the latter [Figure 1]. Fetal surgery has opened new dimensions in pediatric surgery and obstetric anesthesia in addition to posing fundamental ethical-legal challenges. This is the first case report on anesthesia for fetoscopy performed in Saudi Arabia.

Figure 1

Fetoscope in the uterine cavity and video screen to visualize the fetus

CASE REPORT

The case focuses on a young primigravid lady who was diagnosed to have a single baby of 24 weeks gestation with a diaphragmatic hernia. Both mother and baby were investigated (blood and imaging) as per the protocol of Obstetrics and Gynecology Department of Prince Sultan Military Medical City. Fetal ultrasound (US) revealed that the liver was located in the chest and due to a head to chest ratio of <1.0, the criteria to undergo fetoscopic endoluminal tracheal occlusion was met.[1] A pre-operative multidisciplinary team meeting to discuss this case was held a week before the procedure, which involved a feto-maternal medicine physician, obstetrician, neonatologist, Anesthetist and otolaryngeal surgeon. Pre-operative assessment of the mother classified her as being a 24-year-old, 27 weaker, ASA 1 lady of average build with a body weight of 82 kg. Her only complaints included mild heart burn and fatigue on moderate exertion. She had never been operated on before or admitted to hospital. Her physiological parameters (heart rate (HR), blood pressure (BP), SpO2,) and laboratory results (hemoglobin, urea and electrolytes, clotting screen, liver function tests and blood sugar) were all in normal range and urine analysis was negative for protein and sugar. There was no history of allergy.

Informed consent for the procedure (which included epidural anesthesia) was obtained from the mother and documented. She was given a first oral dose of ranitidine 150 mg pre-operatively and 12 h later a second dose was given in addition to oral metoclopramide 10 mg. She was also requested to drink 30 ml of sodium citrate prior to transferring her to the theater. Following routine check-up in the operating theater, she was brought to the recovery room. Here, she was connected to standard (electrocardiography, BP and pulse oximeter) monitors that revealed normal heart rhythm at a rate of 90/min, BP of 112/76 mmHg and SpO2 Of 98% at room air. An intravenous (IV) line was established in her left hand and connected to a running drip (200 ml/h) of Ringer's lactate solution. Tocolytic therapy was commenced with Atociban (Tractocile™ an oxytocin inhibitor) bolus dose of 0.9 ml (6.5 mg) over 1 min followed by an infusion of 24 ml/h (=18 mg/h) to be given over 3 h. Administration of the bolus dose of Atociban resulted in transient mild changes in HR (100/min, regular sinus rhythm) and BP (106/74) that responded to a bolus of 100 ml of crystalloid.

She was then assisted to adopt a sitting posture for the epidural procedure, which was performed under full aseptic precautions with Arrow™ epidural set using loss of resistance to air technique between L2 and L3 lumbar interspace. An epidural catheter was inserted easily and having left a length of 4 cm in the space, secured with dressing tape. Subsequently, she was placed in a supine position with a 30° left lateral tilt. After confirming a negative catheter aspiration for cerebrospinal fluid and blood, a test dose of 3.0 ml of lignocaine 1.5% with adrenaline (5.0 μg/ml) was injected; upon ruling out catheter placement in the vascular or subarachnoid space, incremental bolus doses of 5.0 ml of bupivacaine 0.5% with fentanyl 5 μg/ml were given at 5 min intervals. Face mask oxygen therapy was started at this stage with Kyoling™ mask at a flow rate of 6 L/min. The total bolus dose of 15 ml was administered over 15 min after the test dose. Her BP was monitored at 5 min intervals and kept at ≥90% of pre-epidural base line systolic BP with co-hydration (IV fluid of ringer's lactate/6% hetastarch with IV boluses of 50 μg of phenylephrine). She received a total of 2 L of fluid (1.5 L of crystalloid and 0.5 L of colloid) and 250 μg of phenylephrine to establish anesthesia during this time (35 min after the last incremental epidural dose). Over the course of this period epidural block, checked repeatedly with ice, had progressed from the lower abdomen to the legs and lower chest. The dermatomal block from S1 to T6 was considered adequate.

She was then transferred to the next door operating theatre. Here, she was placed on the table in the position described above and reconnected to the same standard monitors and IV infusions. A drape curtain was raised in front of the patient. After this, the surgeon performed external cephalic version on the fetus. Once the desired fetal position is achieved, pancuronium (0.2 μg/kg), atropine (20 μg/kg) and fentanyl (15 μg/kg) are given by ultrasound-guided intramuscular injection which provided fetal anesthesia, immobilization and prevention of fetal bradycardia The mother's abdomen was cleaned with antiseptic solution and a curtain drape was raised in front of her chest. At the dermatomal level of T10, a small incision was made on the antro-left lateral side of her abdomen. Under US guidance, a trocar was inserted into her uterus and a fetoscope inserted through this. With the aid of US and real-time video footage that was now appearing on the screen, the surgeon inserted the fetoscope through the fetus’ mouth, larynx and trachea and with the balloon occluded the lumen above the carina [Video 1]. The whole procedure took ½ h. Throughout, patient was informed about what was happening. She appeared relaxed and slightly drowsy (probably due to regional block and from the systemic effect of fentanyl); aside from mild nausea, she had no complaints.

After the procedure, patient was taken to the recovery room for routine monitoring and care. The fetus was also monitored for HR and uterine activity. The Atociban infusion was continued as per protocol. The epidural catheter was removed and she was comfortably placed in a semi-sitting and semi-lateral position. After 45 min, she was transferred to the ward.

DISCUSSION

Fetal surgery holds great promise for obstetric anesthesia and is predicted to become a routine procedure in the USA by the year 2020 for correctable congenital anomalies of the fetus.[2] The important issues in anesthesia for fetal surgery are related both to the mother who is a bystander or a secondary patient and to the fetus who is the primary patient. Such issues can be considered under the following headings: Physiological and anatomical changes in pregnancy, tocolytic medications and their interactions with anesthesia, anesthetizing/sedating the primary patient and finally ethical issues.

Physiological and anatomical changes in pregnancy

Pregnancy-induced maternal changes pose hazards for the mother due to alterations in her anatomy and physiological functions that affect almost every system of her body, but critically the respiratory, cardiovascular, gastrointestinal and central nervous systems. In this case, all prophylactic measures were taken to avoid acid aspiration to the lung. By not using general anesthesia, risks to the mother's airway and complications related to laryngoscopy, intubation and extubation were avoided. Placement in the supine position with left lateral tilt during the peri-operative period prevented the development of supine hypotension. Full doses were given incrementally as this is recommended to be the safest technique. Furthermore, the desired height of the dermatomal block for fetoscopy was assumed to be less than that for cesarean section. The reasons for this assumption were (a) uterus would be relaxed and (b) less pressure and traction would be applied on the uterus during fetoscopy. As opposed to the upper level of dermatomal block (T4) recommended for cesarean section, we aimed for the T6 region for fetoscopy.

Tocolytic medications and their interactions with anesthesia

Tocolytic medications are used to relax the uterus, which facilitates fetal intervention in addition to preventing the development of premature labor. These drugs belong to various pharmacological groups and include beta-adrenergics (Ritrodrine, Salbutamol), calcium channel blockers (Nifedipine), anticonvulsants/antiarrythmics (Magnesium sulphate), Non-steroidal anti-inflammatory drugs (ibuprofen) and oxytocin/vasopressin antagonists (Atosiban); the latter was used by the feto-maternal physician in this case. Most commonly used tocolytic drugs for fetoscopic procedure are ß-adrenoceptor agonists, nifedipine and magnesium sulfate.[3] However, atosiban was used by the feto-maternal physician in this case. Though, it is more expensive than the other tocolytic agents, but possess fewer serious cardio-respiratory side-effects.[4]

Theoretically, the interaction of epidural anesthesia with tocolytic drugs is synergistic in dilating maternal blood vessels. In anticipation, we commenced the cohydration of IV fluids (crystalloid/colloid) with the administration alpha-mimetics (phenylephrine) and titrated so as to maintain a maternal systolic BP of 90-100% of the baseline value. This ensured adequate uterine perfusion and hence fetal wellbeing. Factors, which decrease uterine blood supply include maternal hypotension or hypertension (the latter due to hyper stimulation of α-adrenergic receptors) and increased myometral tone. Inhalational vapor anesthesia, but not total intravenous anesthesia or regional anesthesia, augments the uterine relaxant effect of tocolytic agents. The disadvantages of epidural anesthesia include lack of fetal anesthesia and lack of uterine relaxation.

Anesthetizing/sedating the primary patient and ethical issues

Pain is considered a subjective phenomenon as a “feeling” of unpleasantness. The inability to express pain should thus not be interpreted as its absence.[5] Up until recently, the management let alone the existence of fetal pain was a contentious issue. There is evidence to suggest that the fetus can experience pain by 20 weeks of gestation;[6] expression of a neuroendocrine stress response to noxious stimuli has been demonstrated.[7] This response can be attenuated by narcotics.[8]

When the mother receives general anesthesia, the fetus is anesthetized as well. However, the fetus is not anesthetized when the mother receives regional anesthesia alone. In cases of the latter, the fetus should be anesthetized/sedated by medications given directly (intramuscular injection) or indirectly (via mother). Importantly when considering anesthesia for the fetus emphasis should be placed on the duration of pain the fetus will experience; will it be for a short time (e.g., needle stick for fetal injection) or a long time (e.g., during fetal surgery).[6] In our case, the intervention was minimum and for a relatively short period. Furthermore, the mother was already relaxed and mildly sedated with epidural block and parenteral absorption of fentanyl. We therefore, felt that there was no need to give additional sedation to the mother.

CONCLUSION

Adequate anesthesia is fundamental to the optimum peri-operative care of the mother and the fetus. The Anesthetist should know the demands and challenges he/she is expected to encounter during this period. This is the first case report describing anesthesia care for fetoscopy performed in Saudi Arabia. Epidural anesthesia with a focus on feto-maternal concerns provides safe and satisfactory conditions for the Laparascopist and both patients.